Hello and welcome aboard... TEBAYANE..
It's nice to have you join the community. Here's a link to your device's area of discussion. http://androidforums.com/samsung-admire/
I'm not sure why would they (MetroPcs) would blocked their phones from being able to connect to WiFi (wireless internet). I would think that this would reduce the load of users using a vast amount of data on they network.
As for wireless tethering, you would have to contact your service provider to find out if this is something they support.
Good luck. And thanks for joining.